The object of this research is: a) to establish organotypic in-vitro systems for the study of human and experimental central and peripheral nervous system tumors, with the view to analyze the factors that affect favorably or adversely cell differentiation and maturation; and b) to study, in the in-vitro systems obtained, the phenomena of cell differentiation, maturation, regression, anaplasia and stroma-induction by morphological methods (light and electron microscopy, special staining and histochemical techniques, immunofluorescence for specific antigen-antibody protein complexes), and by biochemical analysis of such systems, including the use of labelled protein, RNA and DNA precursors and, in the case of neuronal tumors, the demonstration of enzymes concerning with the synthesis and degradation of neurotransmitter substances. The techniques to be employed are those that have been developed in this laboratory for the study of nervous system tumors in organ and tissue culture systems, i.e., a three-dimensional sponge foam matrix technique; a Millipore filter platform technique; and a collagen-coated coverslip technique.